It is the long-range goal of this investigation to elucidate the mechanism of action of FSH upon the mammalian testis and thus provide a link between hormonal modulation of genetic information and the physiological function of the organ involved. In this manner it is hoped to gain some insight into the problem of the control and regulation of the male reproduction process. The specific tasks involved are to determine the site of action of FSH within the rat testis and the sequence of biochemical events which are set into motion soon after this hormone interacts with the target cell. Finally, these initial biochemical events will be related to the later actions of this gonadotrophin. It is hoped that effect of FSH upon mitotic activity and/or androgen-binding protein synthesis may provide the long-awaited link between the early stimulation of biochemical events and a possible physiologic role for this hormone. BIBLIOGRAPHIC REFERENCES: O'Malley, B.W., Woo, S.L.C., Harris, S.E., Rosen, J.M. and Means, A.R. (1975) Steroid Hormone Regulation of Specific Messenger RNA and Protein Synthesis in Eucaryotic Cells. J. Cell Physiol. 85: 343-356. Harris, S.E., Rosen, J. M., Means, A.R. and O'Malley, B.W. (1975) Use of a Specific Probe for Ovalbumin Messenger RNA to Quantitate Estrogen-Induced Gene Transcripts. Biochemistry 14:2072-2081.